JPH0785410A - Apparatus and method for controlling head of magnetic disk apparatus - Google Patents

Abstract

PURPOSE:To realize a countermeasure which ensure the reliability of recorded data even when the head crashes against the disk over an allowable level by monitoring the crash between the head and disk. CONSTITUTION:A sensor 4 formed out of a piezoelectric element member and provided at a slider outputs a detecting signal corresponding to a shock force when a head 1 crashes against a disk 2. When the detected shock force is outside an allowable range, a CPU 6 controls the head 1 to execute a write operation again if the head 1 is writing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a head controller for a magnetic disk device which is a hard disk device.

[0002]

2. Description of the Related Art Conventionally, in a hard disk drive (HDD), a head seeks to a target track on a disk that is rotating at high speed, and data is read / written on the data surface of the disk. A large number of tracks are formed on the data surface, and each track is further divided into a plurality of sectors.

Here, in the HDD, when performing seek or read / write on the data surface, the slider of the head is in a state of being lifted by a predetermined flying amount, and is in a non-contact state with the surface of the disk. .

On the other hand, when the HDD power is off, non-read / write
During the write operation, the head is positioned in the CSS (contact start stop) zone provided on the innermost side of the disk. In the CSS zone, the head is in contact with the surface of the disk. When the power of the HDD is turned on and the disk starts to rotate at high speed, the slider of the head floats above the CSS zone due to the dynamic air pressure caused by the high speed rotation of the disk.

By the way, HDDs are made smaller (especially thinner).
Higher recording density is being promoted. With higher recording density,
Electromagnetic converter of head (core with magnetic gap)
It is effective to reduce the distance between the disk and the disk surface.
Therefore, the slider of the head is improved so as to fly while maintaining a minute gap with respect to the disk surface.

However, if the gap between the head and the disk surface is made small, the probability that the slider will collide with a minute projection on the disk surface is extremely increased. When the slider collides with the protrusion during the read / write operation, the flying posture of the head becomes unstable and the read / write operation becomes unstable. Further, the collision causes a defect in the magnetic film of the disk, which makes it impossible to write data in that portion. Further, when the head and the minute pieces of the disk are dispersed on the disk surface due to the collision, a defective part of the disk may be enlarged or a worst case such as head crash (breakage) may occur.

[0007]

Due to the higher recording density of HDDs, the flying height of the head with respect to the disk surface has become extremely small. Therefore, the slider of the head is more likely to collide with a minute projection on the disk surface, which causes unstable read / write operations, generation of defective parts on the disk surface, and head crash.
Due to such factors, the reliability of the data recorded on the disc is impaired. Suppression of minute protrusions on the disk surface has also been studied, but sufficient results have not been obtained at this time.

An object of the present invention is to monitor a collision between a head and a disk, and when a collision exceeding an allowable range occurs,
It is to realize a measure that can ensure the reliability of recorded data.

[0009]

SUMMARY OF THE INVENTION The present invention comprises a piezoelectric element member provided on, for example, a slider of a head means, a detection means for detecting an impact force due to a collision between a head and a disk, and an impact force outside an allowable range. In this case, the head control device of the magnetic disk device is provided with a collision control means for executing a predetermined process.

[0010]

In the present invention, the detection means formed of the piezoelectric element member provided on the slider outputs a detection signal corresponding to the impact force when the head and the disk collide. The collision control means controls to re-execute the write operation if the head is in the write operation when the impact force detected by the detection means is outside the allowable range.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a main part of an HDD according to the embodiment, FIG. 2 is a perspective view for explaining a structure of a head according to the embodiment, and FIG. 3 is a flow chart for explaining an operation of the embodiment. Is.

As shown in FIG. 1, the HDD comprises a disk 2 which is rotating by a spindle motor 3 and a head 1 which levitates above the surface of the disk 2 and performs a data read / write operation. Spindle motor 3
Are driven by a motor driver 8 controlled by a control circuit (CPU) 6.

The head 1 is supported by a head actuator (carriage) (not shown) and is moved in the radial direction of the disk 2. The head 1 executes a read / write operation by the read / write circuit system 5. The read / write circuit system 5 supplies a write current according to the write data to the head 1 and executes a data reproducing operation from a read signal from the head 1.

Further, in this embodiment, the head 1 is provided with an impact force sensor 4 composed of a piezoelectric element member. Specifically, as shown in FIG. 2, the impact force sensor 4 is provided on the slider 1b, for example, on the side opposite to the disk surface (the direction of the arrow). The slider 1b is the main body of the head 1,
It has an electromagnetic converter (magnetic gap, coil, core) 1a, and floats from the disk surface by air dynamic pressure. The slider 1b is supported by the suspension 10 of the head actuator.

The impact force sensor 4 outputs a detection signal to the impact detection circuit 7. The shock detection circuit 7 is, as shown in FIG.
An amplifier 7a that amplifies the detection signal and a level detection circuit 7 that detects the voltage level of the detection signal and converts it to digital
b. The level detection circuit 7b converts the voltage level corresponding to the detected impact force into digital data and C
Output to PU6. The CPU 6 measures the impact degree by the level (digital data) of the input detection signal according to a program and measurement data prepared in advance, and determines whether or not the impact degree exceeds the allowable range. Various controls are executed based on this determination result.

Next, the operation of the embodiment will be described. First,
When the HDD is powered on and started up, the spindle motor 3 is driven by the control of the CPU 10 to rotate the disk 2. At this time, the head 1 is in contact with the CSS zone of the disk 2 and stopped.

When the rotational movement of the disk 2 becomes high, the slider 1b of the head 1 is moved to C by the air dynamic pressure.
It will be in a state of rising from the SS zone. The head 1 moves from the CSS zone toward the target track in a floating state (step S1 in FIG. 3). CPU6
The head actuator is controlled so as to position the head 1 on the target track according to the operation of a servo circuit (not shown). The head 1 executes a data read / write operation on a target track according to the operation of the read / write circuit system 5 (step S2).

Here, the slider 1b of the head 1 maintains a state of floating above the surface of the disk 2 with a minute gap. At this time, it is assumed that the slider 1b collides with a minute projection on the surface of the disk 2 due to, for example, an impact from the outside of the HDD. Due to the piezoelectric effect of the piezoelectric element member, the sensor 4 converts the impact force caused by the collision into an electric signal and outputs it as a detection signal.

When the detection signal from the sensor 4 is input, the impact detection circuit 7 converts the voltage level corresponding to the impact force detected by the level detection circuit 7b into digital data and outputs it to the CPU 6 (step S3). CPU6
The impact degree is measured based on the level of the detection signal, and it is determined whether the impact degree exceeds the allowable range (step S4).
If the determination result is within the allowable range, the CPU 6 continues the operation such as the read / write operation (step S).
6).

On the other hand, if the judgment result exceeds the permissible range, the CPU 6 executes the following processing, and as a result, the reliability of the recorded data on the disk 2 is ensured. That is, when the head 1 is in the write operation, the CPU 6 re-executes the write operation via the HDC (disk controller) not shown (YES in step S7, S8). This is because the flying height of the head 1 may fluctuate due to a collision and the normal write operation may not be completed, so that data can be surely recorded by another write operation.

Next, when the CPU 6 detects an impact degree exceeding a permissible range for a certain time or longer, it determines that a worst situation such as head crash has occurred and stops the operation of the HDD (steps S9 to S12). ). In this case, HD
The process of notifying the host computer through C is also performed.

Further, when the impact degree exceeding the allowable range is continuously detected, the CPU 6 determines that an irrecoverable defect has occurred on the surface of the disk 2. Based on this determination result, for example, an alternative sector or an alternative track (alternative cylinder)
The conventional defect processing for setting is executed. Alternatively, the operation of the HDD may be stopped and the process of instructing the exchange of the disk may be executed through the host computer.
In the defect processing, the head 1 is positioned in the alternative sector or cylinder instead of using the defective sector or cylinder, and the data write operation is executed.

[0023]

As described above in detail, according to the present invention, the collision between the head and the disk is monitored, and when the impact exceeds the allowable range, the write operation is re-executed, the device is stopped, or Various processes such as defect processing are executed. Therefore, it is possible to ensure the reliability of the data recorded on the disc as a result.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part of an HDD according to an embodiment of the present invention.

FIG. 2 is a perspective view for explaining the structure of the head according to the embodiment.

FIG. 3 is a flowchart for explaining the operation of the embodiment.

[Explanation of symbols]

1 ... Head, 2 ... Disk, 4 ... Impact force sensor, 6 ... C
PU, 7 ... Impact detection circuit.

Claims (4)

[Claims] 1. A detection method comprising head means for reading / writing data from / to a disk, and a piezoelectric element member provided on the head means, for detecting an impact force when the head means collides with the disk. A head control device for a magnetic disk drive, comprising: means and a collision control means for executing a predetermined process on the head means when the impact force detected by the detection means is outside an allowable range. 2. Detecting a head means for reading / writing data from / to a disk, and a piezoelectric element member provided in the head means, for detecting an impact force when the head means collides with the disk. And a control unit that re-executes the write operation by the head unit when the impact force detected by the detection unit is out of the allowable range and the head unit is in the write operation. Head controller for magnetic disk drive. 3. A detection device having head means for reading / writing data from / to a disk and a piezoelectric element member provided to the head means, and detecting an impact force when the head means collides with the disk. And a control means for stopping the read / write operation when the impact force detected by the detecting means is outside the permissible range and the detection of the impact force outside the permissible range continues for a certain time or longer. A head control device for a magnetic disk drive characterized by the above. 4. A magnetic disk device for executing a read / write operation in a state where a head is in contact with a rotating disk, and a shock when the head and the disk collide with each other, by a detection means composed of a piezoelectric element member. A step of detecting a force, a step of determining whether or not the detected impact force is outside an allowable range, and a step of determining whether the impact force is outside the allowable range and the head is a write operation A magnetic disk device comprising: a step of re-executing a write operation; and a step of stopping the read / write operation by the head when the detection of the impact force outside the allowable range continues for a certain time or more. Head control method.